This invention generally relates to slider-operated flexible zippers for use in reclosable pouches, bags or other packages of the type in which perishable material, such as foodstuff, may be stored.
Reclosable fastener assemblies are useful for sealing thermoplastic pouches or bags. Such fastener assemblies often include a plastic zipper and a slider. Typically, the plastic zippers include a pair of interlockable fastener elements, or profiles, that form a closure. As the slider moves across the profiles, the profiles are opened or closed. The profiles in plastic zippers can take on various configurations, e.g. interlocking rib and groove elements having so-called male and female profiles, interlocking alternating hook-shaped closure elements, etc.
In one type of slider-operated zipper assembly, the slider straddles the zipper and has a separating finger at one end that is inserted between the profiles to force them apart as the slider is moved along the zipper in an opening direction. The other end of the slider is sufficiently narrow to force the profiles into engagement and close the zipper when the slider is moved along the zipper in a closing direction.
Other types of slider-operated zipper assemblies avoid the use of a separating finger. For example, U.S. Pat. No. 6,047,450 discloses a zipper comprising a pair of mutually interlockable zipper profiles, portions of which form a fulcrum about which the zipper halves may be pivoted out of engagement. This is accomplished by a slider that straddles the zipper and has an opening end designed to force lower edges of the bases of the zipper halves towards each other, causing the interlocked zipper profiles to pivot in opposite directions about the fulcrum point and thereby disengage.
It is also known to provide sliders that do not straddle the zipper. For example, U.S. patent application Ser. No. 10/175,188 discloses a slider-operated zipper assembly for reclosable packaging in which the slider is mounted inside the zipper. This slider-zipper assembly design allows packaging film to be sealed directly to the exterior or backs of the zipper parts without interfering with the operation of the slider. Being able to seal the packaging film to the outside of the zipper parts makes it easier to incorporate header features that are typically used to provide evidence of tampering. Conventional extension flanges are not needed when the packaging film is joined to the backs of the zipper profiles.
There is a need for further improvements in slider-zipper assembly designs that allow packaging film to be sealed directly to the exterior of the zipper parts.